Spatial Orientation‐Dependent Double Hydrogen Bond/Photoredox Cooperative Catalysis in Metal–Organic Frameworks

Abstract

ABSTRACT Catalyst activity is typically the primary priority in designing a catalytic system. The higher catalyst activity is envisioned to confer more powerful and effective catalytic performance. Here, we report a heterogeneous double hydrogen bond/photoredox synergistic catalysis, wherein the flexibility and spatial orientation of catalytic centers, rather than catalyst activity, play a dominant role in catalytic performance. We synthesized six metal–organic frameworks (MOFs) with photocatalytic and double hydrogen bond donor (DHBD) centers. MOF‐F‐TU featuring the relatively flexible (F) thiourea (TU) center has proved most effective in promoting dehalogenation and reductive coupling reactions. In contrast, MOF‐R‐SQA1 with a stronger but rigid (R) squaramide (SQA1) site exhibits no catalytic activity. Mechanistic studies rationalize this unique phenomenon by implying a cooperative activation of the substrate via its double hydrogen bonding with DHBD and π–π overlapping with photocatalytic center, which is closely associated with the spatial arrangement of synergistic catalytic centers. MOF‐F‐TU also outperforms homogeneous counterparts, displaying turnover numbers of up to 9500.